Connective tissue is the main determinant of the mechanical properties of the lungs and is also thought to play a major role in the exchange of nutrients and metabolites between the capillary and epithelial cells and in the diffusion of O2 and CO2 between the alveolar gas and the blood. Proteoglycans represent only a small portion of the connective tissue of lung parenchyma, but, perhaps through interactions with collagen and elastin, are thought to play an important role in the maintenance of the structural and functional integrity of this tissue. The purposes of this project are: 1) to find efficient methods to extract and purify PG of lung parenchyma; 2) to isolate and characterize the soluble PG by chemical, physical and immunological methods; 3) to identify the PG resisting extraction; 4) to study possible interactions between soluble and insoluble PG and collagen. We plan to use animal lungs in this phase of our study, since this tissue does not present problems of availability of quantity. The knowledge acquired from animal tissue will eventually be applied to the study of human normal and diseased (particularly emphysematous) lungs.